Frank, It will all depends on the area that you are hunting. Relic hunting, old homes, old parks, you will want to dig all non-ferrous targets. In a real life situation, at old homes, I will dig an average of 1 good target to 4- 5 bad targets. But there is something that you have to remember, all jewelry, coins, buttons, etc will be dug that could easily be missed with a detector running more discrimination or a notch. A lot of foil targets will be pinky rings, ear rings, etc., while targets between nickels and zincs will be dug, resulting in considerable more jewelry. Some coins will apply here too since at depth, they may fall out of the coin range..Extended discrimination detectors, will call these targets as bad since all they can see is that there is a target there.
The person will let it go since the detector has "mis-informed him because of a lack of information. With the Deeptech, you will dig... I hope this helps... Richard